I've answered my own question having now experienced AKL-SFO-LHR in Y as Air NZ Gold ticketed via VS.

In Auckland full *G benefits as flying with Air NZ as carrier.

In San Francisco I received priority standby for free on an earlier VS flight at my request, Sky Priority to clear security, and access to the Clubhouse Lounge with no questions asked at all. In fact there was a lounge agent furiously turning back all the travellers in front of me, but said nothing as I scanned my BP for entry.

Honestly this is not at all what I was expecting, what a great experience.

On the way back in three weeks I'll see how it goes accessing clubhouse in both LHR and SFO.